1. Field of the Invention
This invention generally relates to a front derailleur for a bicycle. More specifically, the present invention relates a front derailleur for a bicycle that can be used with many different shapes of bicycle frames.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One part of the bicycle that has been extensively redesigned is the frame of the bicycle. In fact, each bicycle manufacturer may have several different frame designs. Accordingly, most bicycle components can not work on all bicycle frames. This requires the bicycle component manufacturers to produce a different bicycle component for different frame designs. For example, most bicycle frames have cable guides (cable housing stoppers) that are welded on the frame tubes at various locations for guiding brake cables and shift cables to their respective components. Depending upon the placement of these cable guides, the configuration of the brake or derailleur may need to be changed.
This problem is particularly present in manufacturing a front derailleur that is mounted onto the bicycle frame adjacent to the front sprockets. Generally, a front derailleur includes a fixed member nonmovably secured to a bicycle frame, and a movable section supported to be movable relative to the fixed member. Typically, the fixed member is a tubular clamping member that is secured to the seat tube. Alternatively, the fixed member is sometimes coupled to the bottom bracket. The movable section has a chain guide with a pair of cage plates for contacting and moving a chain between the front sprockets.
The movable section is movable relative to the fixed member by pulling a shift control cable. In particular, the movable section and fixed member usually are interconnected through pivotal links. The control cable is connected to one of the pivotal links to apply a torque thereto, thereby causing the links to move the movable section. The control cable is fixedly coupled to the link in such a position that an operating force is applied to the control cable. This force on the cable is converted into a link swinging torque. Depending on the arrangement and locations of the cable guides, the cable attachment member of the front derailleur may needed to be configured differently for different types of frames.
In particular, some manufacturers have the front shift cable directed to the top of the front derailleur, while other manufacturers have the front shift cable directed to the bottom of the front derailleur. If the front shift cable is directed to the top of the front derailleur, then cable guides are welded along the top tube and the seat tube. If the front shift cable is directed to the bottom of the front derailleur, then cable guides are welded along the down tube.
This presents a problem for many bicycle component manufacturers as well as for bicycle shops that carry a full line of bicycle components. In particular, two types of front derailleurs now must be manufactured. One type of front derailleur that accommodates an upwardly pulled front shift cable and another type of front derailleur that accommodates a downwardly pulled front shift cable. Accordingly, most component manufacturers produce an upwardly pulled type front derailleur and a downwardly pulled type front derailleur. In some cases, derailleurs have been produced that can be used for both upwardly and downwardly pulled front shift cable. However, the shift cables of these front derailleurs are often pulled at sharp angles from the cable attachment points. This can result in excessive stress on the inner wire of the shift cable.
In view of the above, there exists a need for a front derailleur for a bicycle, which can be used with either an upwardly pulled front shift cable or a downwardly pulled front shift cable. Moreover, there exists a need for a front derailleur that minimizes stress on the inner wire of the shift cable whether the inner wire is being pulled upwardly or downwardly. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.